FIELD OF THE INVENTION
[0001] My invention relates to methods and apparatuses for manufacturing paper products
such as paper towels and bathroom tissue. In particular, my invention relates to a
molding roll to mold a paper web during the formation of the paper product.
BACKGROUND OF THE INVENTION
[0002] Generally speaking, paper products are formed by depositing a furnish comprising
an aqueous slurry of papermaking fibers onto a forming section to form a paper web,
and then dewatering the web to form a paper product. Various methods and machinery
are used to form the paper web and to dewater the web. In papermaking processes to
make tissue and towel products, for example, there are many ways to remove water in
the processes, each with substantial variability. As a result, the paper products
likewise have a large variability in properties.
[0003] One such method of dewatering a paper web is known in the art as conventional wet
pressing (CWP). Figure I shows an example of a CWP papermaking machine 100. Papermaking
machine 100 has a forming section 110, which, in this case, is referred to in the
art as a crescent former. The forming section 110 includes headbox 112 that deposits
an aqueous furnish between a forming fabric 114 and a papermaking felt 116, thereby
initially forming a nascent web 102. The forming fabric 114 is supported by rolls
122, 124, 126, 128. The papermaking felt 116 is supported by a forming roll 120. The
nascent web 102 is transferred by the papermaking felt 116 along a felt ran 118 that
extends to a press roll 132 where the nascent web 102 is deposited onto a Yankee dryer
section 140 in a press nip 130. The nascent web 102 is wet-pressed in the press nip
130 concurrently with the transfer to the Yankee dryer section 140. As a result, the
consistency of the web 102 is increased from about twenty percent solids just prior
to the press nip 130 to between about thirty percent solids and about fifty percent
solids just after the press nip 130. The Yankee dryer section 140 comprises, for example,
a steam filled drum 142 ("Yankee drum") and hot air dryer hoods 144, 146 to further
dry the web 102. The web 102 may be removed from the Yankee drum 142 by a doctor blade
152 where it is then wound on a reel (not shown) to form a parent roll 190.
[0004] A CWP papermaking machine, such as papermaking machine 100, typically has low drying
costs, and can quickly produce the parent roll 190 at speeds from about three thousand
feet per minute to in excess of five thousand feet per minute. Papermaking using CWP
is a mature process that provides a papermaking machine having high runability and
uptime. As a result of the compaction used to dewater the web 102 at the press nip
130, the resulting paper product typically has a low bulk with a corresponding high
fiber cost. While this can result in rolled paper products, such as paper towels or
toilet paper, having a high sheet count per roll, the paper products generally have
a low absorbency and can feel rough to the touch.
[0005] As consumers often desire paper products that feel soft and have a high absorbance,
other papermaking machines and methods have been developed. Through-air-drying (TAD)
is one method that results in paper products with high bulk. Figure 2 shows an example
of a TAD papermaking machine 200. The forming section 230 of this papermaking machine
200 is shown with what is known in the art as a twin-wire forming section and it produces
a sheet similar to the crescent former 110 of Figure I. As shown in Figure 2, the
furnish is initially supplied in the papermaking machine 200 through a headbox 202.
The furnish is directed by the headbox 202 into a nip formed between a first forming
fabric 204 and a second forming fabric 206, ahead of forming roll 208. The first forming
fabric 204 and the second forming fabric 206 move in continuous loops and diverge
after passing beyond forming roll 208. Vacuum elements such as vacuum boxes, or foil
elements (not shown) can be employed in the divergent zone to both dewater the sheet
and to insure that the sheet stays adhered to second forming fabric 206. After separating
from the first forming fabric 204, the second forming fabric 206 and web 102 pass
through an additional dewatering zone 212 in which suction boxes 214 remove moisture
from the web 102 and second forming fabric 206, thereby increasing the consistency
of the web 102 from, for example, about ten percent solids to about twenty-eight percent
solids. Hot air may also be used in dewatering zone 212 to improve dewatering. The
web 102 is then transferred to a through-air drying (TAD) fabric 216 at transfer nip
218, where a shoe 220 presses the TAD fabric 216 against the second forming fabric
206. In some TAD papermaking machines, the shoe 220 is a vacuum shoe that applies
a vacuum to assist in the transfer of the web 102 to the TAD fabric 216. Additionally,
so-called rush transfer maybe used to transfer the web 102 in transfer nip 218 as
well as structure it. Rush transfer occurs when the second forming fabric 206 travels
at a speed that is faster than the TAD fabric 216.
[0006] The TAD fabric 216 carrying the paper web 102 next passes around through-air dryers
222, 224 where hot air is forced through the web to increase the consistency of the
paper web 102, from about twenty-eight percent solids to about eighty percent solids.
The web 102 is then 10 transferred to the Yankee dryer section 140, where the web
102 is further dried. The sheet is then doctored off the Yankee drum 142 by doctor
blade 152 and is taken up by a reel (not shown) to form a parent roll (not shown).
As a result of the minimal compaction during the drying process, the resulting paper
product has a high bulk with corresponding low fiber cost. Unfortunately, this process
is costly to operate because a lot of water is removed by 15 expensive thermal drying.
In addition, the papermaking fibers in a paper product made by TAD typically are not
strongly bound, resulting in a paper product that can be weak.
[0007] Other methods have been developed to increase the bulk and softness of the paper
product as compared to CWP, while still retaining strength in the paper web and having
low drying costs as compared to TAD. These methods generally involve compactively
dewatering the wet 20web and then belt creping the web so as to redistribute the web
fibers in order to achieve desired properties. This method is referred to herein as
belt creping and is described in, for example,
U.S. Patent No. 7,399,378,
No. 7,442,278,
No. 7,494,563,
No. 7,662,257, and
No. 7,789,995 (the disclosures of which are incorporated by reference in their entirety).
[0008] Figure 3 shows an example of a papermaking machine 300 used for belt creping. Similar
to the CWP papermaking machine 100, shown in Figure I, the belt creping papermaking
machine 300 uses a crescent former, discussed above, as the forming section 110. After
leaving the forming section 110, the felt run 118, which is supported on one end by
roll 108, extends to a shoe press section 310. Here, the web 102 is transferred from
the papermaking felt 116 to a backing roll 312 in a nip formed between the backing
roll 312 and a shoe press roll 314. A shoe 316 is used to load the nip and dewater
the web 102 concurrently with the transfer.
[0009] The web 102 is then transferred onto a creping belt 322 in a belt creping nip 320
by the action of the creping nip 320. The creping nip 320 is defined between the backing
roll 312 and the creping belt 322, with the creping belt 322 being pressed against
the backing roll 312 by a creping roll 326. In the transfer at the creping nip 320,
the cellulosic fibers of the web 102 are repositioned and oriented. The web 102 may
tend to stick to the smoother surface of the backing roll 312 relative to the creping
belt 322. Consequently, it may be desirable to apply release oils on the backing roll
312 to facilitate the transfer from the backing roll 312 to the creping belt 322.
Also, the backing roll 312 may be a steam heated roll. After the web 102 is transferred
onto the creping belt 322, a vacuum box 324 may be used to apply a vacuum to the web
102 in order to increase sheet caliper by pulling the web 102 into the creping belt
322 topography.
[0010] It generally is desirable to perform a rush transfer of the web 102 from the backing
roll 312 to the creping belt 322 in order to facilitate transfer to creping belt 322
and to further improve sheet bulk and softness. During a rush transfer, the creping
belt 322 is traveling at a slower speed than the web 102 on the backing roll 312.
Among other things, rush transferring redistributes the paper web 102 on the creping
belt 322 to impart structure to the paper web 102 to increase bulk and to enhance
transfer to the creping belt 322. After this creping operation, the web 102 is deposited
on a Yankee drum 142 in the Yankee dryer section 140 in a low intensity press nip
328. As with the CWP papermaking machine 100 shown in Figure I, the web 102 is then
dried in the Yankee dryer section 140 and then wound on a reel (not shown). While
the creping belt 322 imparts desirable bulk and structure to the web 102, the creping
belt 322 may be difficult to use. As the creping belt 322 moves through its travel,
the belt bends and flexes, resulting in fatigue of the creping belt 322. Thus, the
creping belt 322 is susceptible to fatigue failure. In addition, creping belts 322
are custom designed elements with no other commercial analog. They are designed to
impart a targeted structure to the paper web, and can be difficult to manufacture
since they are a low volume element and little prior commercial history exists. Further,
the speed of the papermaking machine 300 is slowed by the crepe ratio when the web
102 is rush transferred from the backing roll 312 to the creping belt 322. The slower
exiting web speed leads to lower production speeds compared to non-belt creped systems.
Additionally, such creping belt runs require large amounts of floor space and thus
increase the size and complexity of thepapermaking machine 300. Furthermore, uniform,
reliable sheet transfer to the creping belt 322 may be challenging to achieve. Accordingly,
there is thus a desire to develop methods and apparatuses that are able to achieve
the paper qualities comparable to fabric creping without the difficulties of the creping
belt.
[0011] EP1541755 A1 discloses a process for producing tissue webs. The process includes the step of partially
dewatering a tissue web and then subjecting the web to multiple deflections against
fabrics prior to drying the tissue web. For instance, in one arrangement, the tissue
web is deflected multiple times in between two opposing fabrics. The tissue web can
be deflected against the fabrics under sufficient pressure to cause the tissue web
to mold against the fabrics. By deflecting the tissue web multiple times, rearrangement
of the papermaking fibers contained in the tissue web occurs increasing the bulk of
the web.
SUMMARY OF THE INVENTION
[0012] In particular, it is provided a roll for molding a fibrous sheet which roll having
the features defined in claim 1. Further preferred arrangements are defined in the
dependent claims. According to one aspect, my invention relates to a roll for molding
a fibrous sheet. The roll includes a cylindrical shell and a vacuum box. The cylindrical
shell is configured to be rotatably driven in a circumferential direction and is permeable
to allow air to be moved through the cylindrical shell. The cylindrical shell has
an interior surface, an exterior surface, and a permeable patterned surface on the
exterior surface of the cylindrical shell. The permeable patterned surface has at
least one of a plurality of recesses and a plurality of projections. The density of
the at least one of the plurality of recesses and the plurality of projections is
greater than about fifty per 0.00064516 square meter (about fifty per square inch).
The vacuum box is positioned on the inside of the cylindrical shell and is configured
to draw air from the exterior surface of the 15 cylindrical shell to the interior
surface of the cylindrical shell. The vacuum box is stationary with respect to the
rotation of the cylindrical shell.
[0013] This and other aspects of my invention will become apparent from the following disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
Figure 1 is a schematic diagram of a conventional wet press papermaking machine.
Figure 2 is a schematic diagram of a through-air-drying papermaking machine.
Figure 3 is a schematic diagram of a papermaking machine used with belt creping.
Figure 4 is a schematic diagram of a papermaking machine configuration of a first
arrangement.
Figure 5 is a schematic diagram of a papermaking machine configuration of the second
arrangement.
Figures 6A and 6B are schematic diagrams of a portion of a papermaking machine configuration
of a third arrangement.
Figures 7 A and 7B are schematic diagrams of a portion of a papermaking machine configuration
of a fourth arrangement.
Figure 8 is a schematic diagram of a portion of a papermaking machine configuration
of a fifth arrangement.
Figures 9A and 9B are schematic diagrams of a portion of a papermaking machine configuration
of a sixth arrangement.
Figures 10A and 10B are schematic diagrams of a portion of a papermaking machine configuration
of a seventh arrangement.
Figures 11A and 11B are schematic diagrams of a portion of a papermaking machine 10
configuration of an eighth arrangement.
Figure 12 is a perspective view of a molding roll of an arrangement.
Figure 13 is a cross-sectional view of the molding roll shown in Figure 12 taken along
the plane 13-13 of Figure 12.
Figure 14 is a cross-sectional view of the molding roll shown in Figure 13 taken along
line 15 14-14.
Figures 15 A, 15B, 15C, 15D, and 15E are arrangements of a permeable shell showing
detail 15 from Figure 14.
Figure 16 is an example of a molding layer of a preferred arrangement of my invention.
Figure 17 is an example of a molding layer of an arrangement.
Figure 18 is a perspective view of a molding roll of an arrangement.
[0015] The arrangement shown in Figs. 6a, b (third arrangement), 7a,b (fourth arrangement),
8 (fifth arrangement), 11a, b (eighth arrangement), and 12 to 15 (ninth arrangement)
are embodiments of the present invention. The further arrangements are explained in
the following as they are helpful for understanding the present invention.
DETAILED DESCRIPTION OF THE PREFERRED ARRANGEMENTS
[0016] My invention relates to papermaking processes and apparatuses that use a molding
roll to produce a paper product. I will describe arrangements of my invention in detail
below with reference to the accompanying figures. Throughout the specification and
accompanying drawings, the same reference numerals will be used to refer to the same
or similar components or features.
[0017] The term "paper product," as used herein, encompasses any product incorporating papermaking
fibers. This would include, for example, products marketed as paper towels, toilet
paper, facial tissues, etc. Papermaking fibers include virgin pulps or recycle (secondary)
cellulosic fibers, or fiber mixes comprising at least fifty-one percent cellulosic
fibers. Such cellulosic fibers may include both wood and non-wood fibers. Wood fibers
include, for example, those obtained from deciduous and coniferous trees, including
softwood fibers, such as northern and southern softwood kraft fibers, and hardwood
fibers, such as 10 eucalyptus, maple, birch, aspen, or the like. Examples of fibers
suitable for making the products of my invention include nonwood fibers, such as cotton
fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw,
jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers. Additional papermaking
fibers could include non-cellulosic substances such as calcium carbonite, titanium
dioxide inorganic fillers, and the like, as well as typical manmade fibers like polyester,
polypropylene, and the like, which may be added intentionally to the furnish or may
be incorporated when using recycled paper in the furnish.
[0018] "Furnishes" and like terminology refers to aqueous compositions including papermaking
fibers, and, optionally, wet strength resins, debonders, and the like, for making
paper products. A variety of furnishes can be used in arrangements of my invention.
In some 20
arrangement furnishes are used according to the specifications described in U.S.
[0019] Patent No. 8,080,130 (the disclosure of which is incorporated by reference in its
entirety). As used herein, the initial fiber and liquid mixture (or furnish) that
is dried to a finished product in a papermaking process will be referred to as a "web,"
"paper web," a "cellulosic sheet," and/or a "fibrous sheet." The finished product
may also be referred to as a cellulosic sheet and or a fibrous sheet. In addition,
other modifiers may variously be used to describe the web at a particular point in
the papermaking machine or process. For example, the web may also be referred to as
a "nascent web," a "moist nascent web," a "molded web," and a "dried web."When describing
my invention herein, the terms "machine direction" (MD) and "cross machine direction"
(CD) will be used in accordance with their well understood meaning in the art. That
is, the MD of a fabric or other structure refers to the direction that the structure
moves on a papermaking machine in a papermaking process, while CD refers to a direction
crossing the MD of the structure. Similarly, when referencing paper products, the
MD of the paper product refers to the direction on the product that the product moved
on the papermaking machine in the papermaking process, and the CD of the product refers
to the direction crossing the MD of the product.
[0020] When describing my invention herein, specific examples of operating conditions for
the paper machine and converting line will be used. For example, various speeds and
pressures will be used when describing paper production on the paper machine. Those
skilled in the art will recognize that my invention is not limited to the specific
examples of operating conditions including speeds and pressures that are disclosed
herein.
10 I. First Arrangement of a Papermaking Machine
[0021] Figure 4 shows a papermaking machine 400 used to create a paper web according to
a first arrangement. The forming section 110 of the papermaking machine 400 shown
in Figure 4 is a crescent former similar to the forming section 110 discussed above
and shown in Figures 1 and 3. An example of an alternative to the crescent 15 forming
section 110 includes a twin-wire forming section 230, shown in Figure 2. In such a
configuration, downstream of the twin-wire forming section, the rest of the components
of such a papermaking machine may be configured and arranged in a similar manner to
that of papermaking machine 400. An example of a papermaking machine with a twin-wire
forming section can be seen in, for example,
U.S. Patent Application Pub. No. 2010/0186913 (the 20disclosure of which is incorporated by reference in its entirety). Still further
examples of alternative forming sections that can be used in a papermaking machine
include a C-wrap twin wire former, an S-wrap twin wire former, or a suction breast
roll former. Those skilled in the art will recognize how these, or even still further
alternative forming sections, can be integrated into a papermaking machine. The nascent
web 102 is then transferred along a felt run 118 to a dewatering section 410. In some
applications, however, a dewatering section separate from the forming section 110
is not required, as will be discussed, for example, in the second arrangement below.
The dewatering section 410 increases the solids content of the nascent web 102 to
form a moist nascent web 102. The preferable consistency of the moist nascent web
102 may vary depending upon the desired application. In this arrangement, the nascent
web 102 is dewatered to form a moist nascent web 102 having a consistency preferably
between about twenty percent solids and about seventy percent solids, more preferably
between about thirty percent solids to about sixty percent solids, and even more preferably
between about forty percent solids to about fifty-five percent solids. The nascent
web 102 is dewatered concurrently with being transferred from the papermaking felt
116 to a backing roll 312. The dewatering section 410 shown uses a shoe press roll
314 to dewater the nascent web 102 against the backing roll 312, as described above
with reference to Figure 3 and in, for example,
U.S. Patent No. 6,248,210 (the disclosure of which is incorporated by reference in its entirety). Those skilled
in the art will recognize that the nascent web 102 may be 10 dewatered using any suitable
method known in the art including, for example, a roll press or a displacement press
as described in my earlier patents,
U.S. Patent No. 6,161,303 and
No. 6,416,631. As discussed further below, the nascent web 102 may also be dewatered using suction
boxes and/or thermal drying. Also as discussed above with reference to Figure 3, the
surface of the backing roll 312 may be heated to assist with transferring the nascent
web 102 15 to the molding roll 420. The backing roll 312 may be heated by using any
suitable means including, for example, a steam heated roll or an induction heated
roll, such as the induction heated roll produced by Comaintel of Grand-Mère, Québec,
Canada. The surface of the backing roll 312 is preferably heated to temperatures between
about two hundred twelve degrees Fahrenheit to about two hundred twenty degrees Fahrenheit.
[0022] After being dewatered, the moist nascent web 102 is transferred from the surface
of the backing roll 312 to a molding roll 420 in a molding zone. In this arrangement,
the molding zone is a molding nip 430 formed between the backing roll 312 and the
molding roll 420. In the molding nip 430, the papermaking fibers are redistributed
by a patterned surface 422 of the molding roll 420 resulting in a paper web 102 that
has variable and patterned fiber orientations and variable and patterned basis weights.
In particular, the patterned surface 422 preferably includes a plurality of recesses
(or "pockets") and, in some cases, projections that produce corresponding protrusions
and recesses in the molded web 102. The molding roll 420 is rotating in a molding
roll direction, which is counterclockwise in Figure 4.
[0023] The use of the molding roll 420 imparts substantial benefits to the papermaking process.
Wet 30 molding the web 102 with the molding roll 420 improves desirable sheet properties
such as bulk and absorbency over paper products produced by CWP shown in Figure I
without the inefficiencies and cost of the TAD process shown in Figure 2. In addition,
the use of the molding roll 420 greatly reduces the complexity of the papermaking
machine 400 and process as compared to processes that use belts to mold the web 102,
such as creping belt 322 shown in Figure 3. Belts are difficult to manufacture and
are limited in the materials that can 5 be used to make a belt with a patterned surface.
Belts require the use of multiple rolls and many different moving parts, which make
belt runs complex, difficult to operate, and introduce a greater number of points
of failure. Belt runs also require a large amount of volume including floor space
within the paper machine and factory. As a result, such belt runs can increase the
costs of an already expensive piece of capital equipment. The molding 10 roll 420
on the other hand is relatively less complex and requires minimal volume and floor
space. Existing CWP machines (see Figure I) can be readily converted to a wet molding
papermaking process by the addition of a molding roll 420 and a backing roll 312.
Because the patterned surface 422 is on or part of the molding roll 420, it does not
need to be designed to withstand bending and flexing that are required for belts.
[0024] In the first arrangement, the moist nascent web 102 may be transferred from the backing
roll 312 to the molding roll 420 by a rush transfer. During a rush transfer, the molding
roll 420 is traveling at a slower speed than the web 102 and the backing roll 312.
In this regard, the web 102 is creped by the speed differential and the degree of
creping is often referred to as the creping ratio. The creping ratio in this arrangement
may be calculated according to 20
Equation (I) as:

where Si is the speed of the backing roll 312 and S2 is the speed of the molding
roll 420. Preferably, the web 102 is creped at a ratio of about five percent to about
sixty percent. But, high degrees of crepe can be employed, approaching or even exceeding
one hundred percent. The creping ratio is often proportional to the degree of bulk
in the sheet, but inversely proportional to the throughput of the paper machine and
thus yield of the papermaking machine 400. In this arrangement, the velocity of the
paper web 102 on the backing roll 312 may preferably be from about one thousand feet
per minute to about six thousand five hundred feet per minute. More preferably velocity
of the paper web 102 on the backing roll 30 is as fast as the process allows, which
is typically limited by the drying section 440. For higher bulk product where a slower
paper machine speeds can be accommodated, a higher creping ratio is used. The molding
nip 430 may also be loaded in order to effect sheet transfer and to control sheet
properties. When rush transfer or other methods, such as vacuum transfer discussed
in the 5 third arrangement below, are used, it is possible to have little or no compression
at the molding nip 430. When molding nip 430 is loaded, the backing roll 312 preferably
applies a load to the molding roll 420 from about twenty pounds per linear inch ("PLI")
to about three hundred PLI, more preferably from about forty PLI to about one hundred
fifty PLI. But, for high strength, lower bulk sheets, those skilled in the art will
appreciate that, in a commercial 10 machine, the maximum pressure may be as high as
possible, limited only by the particular machinery employed. Thus, pressures in excess
of one hundred fifty PLI, five hundred PLI, or more may be used, if practical, and,
when a rush transfer is used, provided the difference in speed between the backing
roll 312 and the molding roll 420 can be maintained and sheet property requirements
are met.
[0025] After being molded, the molded web 102 is transferred to a drying section 440 where
the web 102 is further dried to a consistency of about ninety-five percent solids.
The drying section 440 may principally comprise a Yankee dryer section 140. As discussed
above, the Yankee dryer section 140 includes, for example, a steam filled drum 142
("Yankee drum") that is used to dry the web 102. In addition, hot air from wet end
hood 144 and dry end hood 146 is 20 directed against the web 102 to further dry the
web 102 as it is conveyed on the Yankee drum 142. The web 102 is transferred from
the molding roll 420 to the Yankee drum 142 at a transfer nip 450. Although the papermaking
machine 400 of this arrangement is shown with a direct transfer from the molding roll
420 to the drying section 440, other intervening processes may be placed between the
molding roll 420 and drying section 440 without deviating from the scope of my invention.
[0026] In this arrangement, transfer nip 450 is also a pressure nip. Here, a load is generated
between the Yankee drum 142 and the molding roll 420 preferably having a line loading
of from about fifty PLI to about three hundred fifty PLI. The web 102 will then transfer
from the surface of the molding roll 420 to the surface of the Yankee drum. At consistencies
from about twenty-five percent to about seventy percent, it is sometimes difficult
to adhere the web 102 to the surface of the Yankee drum 142 firmly enough so as to
thoroughly remove the web 102 from the molding roll 420. In order to increase the
adhesion between the web 102 and the surface of the Yankee drum 142 as well as improve
crepe at doctor blade 152, an adhesive may be applied to the surface of the Yankee
drum 142. The adhesive can allow for high velocity operation of the system and high
jet velocity impingement air drying, and also allow for 5 subsequent peeling of the
web 102 from the Yankee drum 142. An example of such an adhesive is a poly(vinyl alcohol)/polyamide
adhesive composition, with an example application rate of this adhesive being at a
rate of less than about forty milligrams per meter squared of sheet. Those skilled
in the art, however, will recognize the wide variety of alternative adhesives, and
further, quantities of adhesives, that may be used to facilitate the 10 transfer of
the web 102 to the Yankee drum 142.
[0027] The web 102 is removed from the Yankee drum 142 with the help of a doctor blade 152.
[0028] After being removed from the Yankee dryer section 140, is taken up by a reel (not
shown) to form a parent roll 190. Those skilled in the art will also recognize that
other operations may be performed on the papermaking machine 400, especially, downstream
of the Yankee drum 15 142 and before the reel (not shown). These operations may include,
for example, calendaring and drawing.
[0029] With use, the patterned surface 422 of the molding roll 420 may require cleaning.
Papermaking fibers and other substances may be retained on the patterned surface 422
and, in particular, the pockets. At any one time during operation, only a portion
of the patterned surface 422 is contacting and molding the paper web 102. In the arrangement
of rolls shown in Figure 4, about half of the circumference of the molding roll 420
is contacting the paper web 102 and the other half (hereafter free surface) is not.
A cleaning section 460 may then be positioned opposite to the free surface of the
molding roll 420 to clean the patterned surface 422. Any suitable cleaning method
and device known in the art may be used. The cleaning section 460 depicted in Figure
4 is a needle jet such as JN Spray Nozzles made by
[0030] Kadant of Westford, MA. A nozzle 462 is used to direct a cleaning medium, such as
a high pressure stream of water and/or a cleaning solution, toward the patterned surface
422 in a direction that opposes the rotating direction of the molding roll 420. The
angle the cleaning medium flows is preferably between a line tangent to the patterned
surface 422 at the point 30 the cleaning medium strikes the patterned surface 422
and perpendicular to the patterned surface 422 at the same point. As a result, the
cleaning medium then chisels and removes anyparticulate matter that has built-up on
the patterned surface 422. The nozzle 462 and stream are located in an enclosure 464
to collect the cleaning medium and particulate matter. Enclosure 464 may be under
vacuum to assist in collecting the cleaning medium and particulate matter.
II. Second Arrangement of a Papermaking Machine
[0031] Figure 5 shows a second arrangement. It has been found that the lower the consistency
of the moist nascent web 102 is when it is molded on the molding roll 420, the greater
affect molding has on desirable sheet properties such as bulk and absorbency. Thus
in general, it is advantageous to minimally dewater the nascent web 102 to increase
10 sheet bulk and absorbency, and in some cases, the dewatering that occurs during
forming may be sufficient for molding. When the web 102 is minimally dewatered, the
moist nascent web 102 preferably has a consistency between about ten percent solids
to about thirty-five percent solids, more preferably between about fifteen percent
solids to about thirty percent solids. With such a low consistency, more of the dewatering/drying
will occur subsequent to 15 molding. Preferably, a non-compactive drying process will
be used in order to preserve as
much of the structure imparted to the web 102 during molding as possible. One suitable
non- compactive drying process is the use of TAD. Among the various arrangements,
the moist nascent web 102 may thus be molded over a range of consistencies extending
from about ten percent solids to about seventy percent solids.
[0032] An example papermaking machine 500 of the second arrangement using a TAD drying section
540 is shown in Figure 5. Although any suitable forming section 510 may be used to
form and dewater the web 102, in this arrangement, the twin wire forming section 510
is similar to that discussed above with respect to Figure 2. The web 102 is then transferred
from the second forming fabric 206 to a transfer fabric 512 at transfer nip 514, where
a shoe 516 presses the transfer fabric 512 against the second forming fabric 206.
The shoe 516 may be a vacuum shoe that applies a vacuum to assist in the transfer
of the web 102 to the transfer fabric 512. The wet web 102 then encounters a molding
zone. In this arrangement, the molding zone is a molding nip 530 formed by roll 532,
the transfer fabric 512, and the molding roll 520. In this arrangement, molding roll
520 and molding nip 530 are constructed and operated similarly to the molding roll
420 and molding nip 430 discussed above with reference to Figure 4. For example, the
web 102 may be rush transferred from the transfer fabric 512 to the molding roll 520
as discussed above and roll 532 maybe loaded into the molding roll 520 to control
sheet transfer and sheet properties. When a speed differential is used, the creping
ratio is calculated using Equation (2), which is similar to Equation (I), as follows:

where S3 is the speed of the transfer fabric 512 and S4 is the speed of the molding
roll 520. Likewise, the molding roll 520 has a permeable patterned surface 522, which
is similar to the patterned surface 422 of the molding roll 420, preferably having
a plurality of recesses (or "pockets") and, in some cases, projections that produce
corresponding protrusions and recesses in the molded web 102.
[0033] Alternatively, the nascent web 102 may be minimally dewatered with a separate vacuum
dewatering zone 212 in which suction boxes 214 remove moisture from the web 102 to
achieve desirable consistencies of about ten percent solids and about thirty-five
percent solids before the sheet reaches molding nip 530. Hot air may also be used
in dewatering zone 212 to improve dewatering.
[0034] After molding, the web 102 is then transferred from the molding roll 520 to a drying
section 540 at a transfer nip 550. As in the papermaking machine 200 discussed above
with reference to Figure 2, a vacuum may be applied to assist in the transfer of the
web 102 from the molding roll 520 to the through-air drying fabric 216 using a vacuum
shoe 552 in the 20 transfer nip 550. This transfer may occur with or without a speed
difference between molding roll 520 and TAD fabric 216. When a speed differential
is used, the creping ratio is calculated using Equation (3), which is similar to Equation
(I), as follows:

where S4 is the speed of the molding roll 520 and Ss is the speed of the TAD fabric
216.
[0035] When rush transfer is used in both the molding nip 530 and the transfer nip 550,
the total creping ratio (calculated by adding the creping ratios in each nip) is preferably
between about five percent to about sixty percent. But as with molding nip 430 (see
Figure 4), high degrees of crepe can be employed, approaching or even exceeding one
hundred percent.The TAD fabric 216 carrying the paper web 102 next passes around through-air
dryers 222, 224 where hot air is forced through the web to increase the consistency
of the paper web 102, to about eighty percent solids. The web 102 is then transferred
to the Yankee dryer section 140, where the web 102 is further dried and, after being
removed from the Yankee dryer section 140 by doctor blade 152, is taken up by a reel
(not shown) to form a parent roll (not shown).
[0036] Wet molding the moist nascent web 102 on the molding roll 520 at consistencies between
about ten percent solids to about thirty-five percent solids produces a premium product
with the associated costs of TAD discussed above, but still retains the other advantages
of using a molding roll 520 including increased bulk and reduced fiber cost.
[0037] Additionally, this configuration gives a means to control so-called sidedness of
the sheet. Sidedness can occur when one side of the paper web 102 has (or is perceived
to have) different properties on one side of the paper web 102 and not the other.
With a paper web 102 made using a CWP paper machine (see Figure I), for example, the
Yankee side of the paper web 102 may be perceived to be softer than the air side because,
as the paper web 102 is pulled from the Yankee drum 142 by the doctor blade 152, the
doctor blade 152 crepes the sheet more on the Yankee side of the sheet than on the
air side of the sheet. In another example, when the paper web 102 is molded on one
side, the side contacting the molding surface may have an increased roughness (e.g.,
deeper recesses and higher protrusions) as compared to the non-molded side. In addition,
the side of a molded paper web 102 contacting the Yankee drum 142 may be further smoothed
when it is applied the Yankee drum 142.
[0038] I have found that the molded structure imparted to the paper web 102 may not continue
through the full thickness of the paper web 102. Transfer of the wet web 102 in molding
nip 530 thus predominately molds a first side 104 of the paper web 102, and transfer
in the transfer nip 550 predominately molds a second side 106 of the paper web 102.
Individually controlling the nip parameters at both the molding nip 530 and the transfer
nip 550 can counteract sidedness. For example, the patterned surface 522 of the molding
roll 520 may be designed with pockets and projections that impart recesses and protrusions
that are deeper and higher, respectively, on the first side 104 of the paper web 102
(prior to the paper web 102 being applied to the Yankee drum 142) than are imparted
by the TAD fabric 216 to the second side 106 of the paper web 102. Then, when the
first side 104 of the paper web 102 is applied to the Yankee drum 142, the Yankee
drum 142 will smooth the first side 104 of the paper web 102 by reducing the height
of the protrusions such that, when the paper web 102 is peeled from the Yankee drum
142 by the doctor blade 152, both the first and second sides 5 104, 106 of the paper
web 102 have substantially the same properties. For example, a user may perceive that
both sides have the same roughness and softness, or commonly measured paper properties
are within normal control tolerances for the paper product. Counteracting sidedness
is not limited to adjusting the patterned structure of the molding roll 520 and the
TAD fabric 216. Sidedness can also be counteracted by controlling other nip parameters
10 including the creping ratio and/or the loading of each nip 530, 550.
III. Third Arrangement of a Papermaking Machine
[0039] Figures 6A and 6B show a third arrangement. As shown in Figure 6A, the papermaking
machine 600 of the third arrangement may have the same forming section 110, dewatering
section 410, and drying section 440 as the papermaking machine 400 15
of the first arrangement shown in Figure 4. Or, as shown in Figure 6B, the papermaking
machine 602 of the third arrangement may have the same forming section 510 and drying
section 540 of the second arrangement shown in Figure 5. The descriptions of those
sections are omitted here. As with the molding rolls 420, 520 of the first and second
arrangements (see Figures 4 and 5, respectively), the molding roll 610 of the third
arrangement has a 20 patterned surface 612 preferably having a plurality of recesses
("pockets"). To improve sheet transfer and sheet molding, the molding roll 610 of
the third arrangement uses a pressure differential to aid the transfer of the web
102 from the backing roll 312 or transfer fabric 512 to the molding roll 610. In this
arrangement, the molding roll 610 has a vacuum section ("vacuum box") 614 located
opposite to the backing roll 312 in Figure 6A or roll 532 in Figure 6B in a molding
zone. In the arrangements shown in Figures 6A and 6B, the molding zone is molding
nip 620. The patterned surface 612 is permeable such that a vacuum box 614 can be
used to establish a vacuum in the molding nip 620 by drawing a fluid through the permeable
patterned surface 612. The vacuum in the molding nip 620 draws the paper web 102 onto
the permeable patterned surface 612 of the molding roll 610 and, in particular, into
30 the plurality of pockets in the permeable patterned surface 612. The vacuum thus
molds the paper web 102 and reorients the papermaking fibers in the paper web 102
to have variable and patterned fiber orientations.
[0040] In other wet molding processes, such as fabric creping (shown in Figure 3), a vacuum
is applied subsequent to the transfer to the creping belt 322 by vacuum box 324. In
this 5 arrangement, however, a vacuum is applied as the paper web 102 is transferred.
By applying the vacuum during the transfer, both the mobility of the fibers during
transfer and the pull of the vacuum increases the depth of fiber penetration into
the pockets of the permeable patterned surface 612. The increased fiber penetration
results in an improved sheet molding amplitude and a greater impact of wet molding
on resultant web properties, such as improved 10 bulk.
[0041] The use of a vacuum transfer allows the molding nip 620 to utilize reduced or no
nip loading. Vacuum transfer may thus be a less-compactive or even a non-compactive
process. Compaction may be reduced or avoided between the projections of patterned
surface 612 and the papermaking fibers located in the corresponding recesses formed
in the web 102. As a 15 result, the paper web 102 may have a higher bulk than one
made from a compactive process, such as fabric creping (shown in Figure 3) or CWP
(shown in Figure I). Reducing the loading at, or not loading, the molding nip 620
can also reduce the amount of wear between the backing roll 312 or transfer fabric
512 and the molding roll 610, as compared to wear between the backing roll 312 and
the creping belt 322 shown in Figure 3. Reducing wear is 20 especially important for
nips that employ rush transfer because increasing crepe ratios (%) and/or increasing
crepe roll loadings tend to increase wear and thus can lead to reduced runtimes.
[0042] Another advantage of using vacuum at the point of transfer is flexibility in the
use of release agents on the backing roll 312 or transfer fabric 512. In particular,
release agents can be reduced or even eliminated. As discussed above, the paper web
102 tends to stick to the smoother of two surfaces during a transfer. Thus, release
agents are preferably used in fabric creping to assist in the transfer of the paper
web 102 from the backing roll 312 to the creping belt 322 (see Figure 3). Release
agents require careful formulation in order to work. They also can build up on the
backing roll 312 or can be retained in the paper web 102. The use of release agents
adds complexity to the papermaking process, reduces the runability of the paper machine
when they are not effective, and may be deleterious to the paper web 102 properties.
In this arrangement, all of these issues can thus be avoided by using vacuum at the
point of transfer from the backing roll 312 or transfer fabric 512 to the molding
roll 610.
[0043] As discussed in the second arrangement, it is preferable for some applications to
wet crepe the moist nascent web 102 when it is very wet (e.g., at consistencies from
about ten percent solids to about thirty-five percent solids). Webs having these low
solid contents may be difficult to transfer. I have found that these very wet webs
may be effectively transferred using vacuum at the point of transfer. And, thus, still
another advantage of molding roll 610 is the ability to wet crepe very wet moist nascent
webs 102 using vacuum box 614. The vacuum level in the molding nip 620 is suitably
large enough to draw the paper web 102 10 from the backing roll 312 or transfer fabric
512. Preferably, the vacuum is from about zero inches of mercury to about twenty-five
inches of mercury, and more preferably from about ten inches of mercury to about twenty-five
inches of mercury.
[0044] Likewise, the MD length of the vacuum zone of the molding roll 610 is large enough
to draw the paper web 102 from the backing roll 312 or transfer fabric 512 and into
the molding 15 surface 612. Such MD lengths may be as small as about two inches or
less. The preferable lengths may depend on the rotational speed of the molding roll
610. The web 102 is preferably subject to vacuum for a sufficient amount of time to
draw the papermaking fibers into the pockets. As a result, the MD length of the vacuum
zone is preferably increased as the rotational speed of the molding roll 610 is increased.
The upper limit of MD length of the 20 vacuum box 614 is driven by the desire to reduce
energy consumption and maximize the area within the molding roll 610 for other components
such as a cleaning section 640. Preferably, the MD length of the vacuum zone is from
about a quarter of an inch to about five inches, more preferably from about a quarter
of an inch to about two inches.
[0045] Those skilled in the art will recognize that the vacuum zone is not limited to a
single vacuum zone, but a multi-zone vacuum box 614 may be used. For example, it may
be preferable to use a two stage vacuum box 614 in which the first stage exerts a
high level vacuum to draw the paper web 102 from the backing roll 312 or transfer
fabric 512 and the second stage exerts a lower level vacuum to mold the paper web
102 by drawing it against the permeable patterned surface 612 and the pockets therein.
In such a two stage vacuum box, the MD 30 length and vacuum level of the first stage
is preferably just large enough to effect transfer of the paper web 102. The MD length
of the first stage is preferably from about a quarter of an inch to about five inches,
more preferably from about a half of an inch to about two inches. Likewise, the vacuum
is preferably from about zero inches of mercury to about twenty-five inches of mercury,
and more preferably from about ten inches of mercury to about twenty 5 inches of mercury.
The MD length of the second stage is preferably larger than the first. Because vacuum
is applied to the paper web 102 over a longer distance, the vacuum can be reduced
resulting in a paper web 102 having higher bulk. The MD length of the second stage
is preferably from about a quarter of an inch to about five inches, more preferably
from about a half of an inch to about two inches. Likewise, the vacuum is preferably
from about ten 10 inches of mercury to about twenty-five inches of mercury, and more
preferably from about fifteen inches of mercury to about twenty-five inches of mercury.
[0046] By drawing a vacuum in molding nip 620, the moist nascent web 102 may be advantageously
dewatered. The vacuum draws out water from the moist nascent web 102, as the web 102
travels on the permeable patterned surface 612 through the vacuum zone (vacuum box
614). Those skilled in the art will recognize that the degree of dewatering is a function
of several considerations including the dwell time of the moist nascent web 102 in
the vacuum zone, the strength of the vacuum, the crepe nip load, the temperature of
the web, and the initial consistency of the moist nascent web 102.
[0047] Those skilled in the art will recognize, however, that the molding nip 620 is not
limited to this design. Instead, for example, features of the molding nip 430 of the
first arrangement or molding nip 530 of the second arrangement may be incorporated
with the molding roll 610 of the third arrangement. For example, it may be desirable
to even further increase the bulk of the paper web 102 by combining the molding roll
610 having the vacuum box 614 with a rush transfer, which further crepes the web 102,
and the vacuum molds it at the same time. The molding roll 610 of the third arrangement
may also have a blow box 616 at transfer nip 630 where the web 102 is transferred
from the permeable patterned surface 612 of the molding roll 610 to the surface of
the Yankee drum 142 or TAD fabric 216. Although blow box 616 provides several benefits
in transfer nip 630, the web may be transferred to the drying section 440, 540 without
it, as discussed above with reference to transfer nip 450 (see 30 Figure 4) or transfer
nip 550 of (see Figure 5). When the drying section is a TAD drying section (see Figure
6B), the web 102 may be transferred in the transfer nip 550 using the blow box 616,
the vacuum shoe 552, or both.
[0048] Positive air pressure may be exerted from the blow box 616 through the permeable
patterned surface 612 of the molding roll 610. The positive air pressure facilitates
the transfer of the molded web 102 at transfer nip 630 by pushing the web away from
the permeable patterned surface 612 of the molding roll 610 and towards the surface
of the Yankee drum 142 (or TAD fabric 216). The pressure in the blow box 616 is set
at a level consistent with good transfer of the sheet to the drying section 440, 540
and is dependent on box size, and roll construction. There should be enough pressure
drop across the sheet to cause it to release from the patterned surface 612. The MD
length of the blow box 616 is preferably from about a quarter of an inch to about
five inches, more preferably from about a half of an inch to about two inches.
[0049] By using a blow box 616, the contact pressure between the molding roll 610 and the
Yankee drum 142 or TAD fabric 216 may be reduced or even eliminated, thus resulting
in less compaction of the web 102 at contact points, thus higher bulk. In addition,
the air pressure from the blow box 616 urges the fibers at the permeable patterned
surface 612 to transfer with the rest of the web 102 to the Yankee drum 142 or TAD
fabric 216, thus reducing fiber picking. Fiber picking may cause small holes (pin
holes) in the web 102.
[0050] Another advantage of the blow box 616 is that it assists in maintaining and cleaning
the patterned surface 612. The positive air pressure through the roll can help to
prevent the accumulation of fibers and other particulate matter on the roll.
[0051] As with the molding rolls 420, 520 of the first and second arrangements, a cleaning
section 640 may be constructed opposite to the free surface of the molding roll 610
(e.g., cleaning section 460 as shown in Figure 4). Any suitable cleaning method and
device known in the art may be used, including the needle jet discussed above. As
an alternative to, or in combination with, a cleaning section 460 constructed opposite
to the free surface, a cleaning section may be constructed inside the molding roll
610 in the section of the molding roll 610 having the free surface. An advantage of
the permeable patterned surface 612 is that cleaning devices may be placed on the
interior of the molding roll to clean by directing a cleaning solution or cleaning
medium outward. Such a cleaning device may include a blow box (not shown) or an air
knife (not shown) that forces pressurized air (as the cleaning medium) though the
permeable patterned surface 612. Another suitable cleaning device may be showers 642,
644 located in the molding roll 610. The showers 642, 644 may spray water and/or a
cleaning solution outward through the permeable patterned surface 612. Preferably,
5 vacuum boxes 646, 648 are positioned opposite to each shower 642, 644 on the exterior
to collect the water and/or cleaning solution.
[0052] Likewise, a receptacle 649, which may be a vacuum box, encloses the showers 642,
644 to collect any water and/or cleaning solution that remains in the interior of
the molding roll 610.
IV. Fourth Arrangement of a Papermaking Machine
[0053] Figures 7A and 7B show a fourth arrangement. As discussed above, molding may be improved
by increasing the mobility of the papermaking fibers in the molding zone, which is
a molding nip 710 in this arrangement. I have found that one way to increase the mobility
of the papermaking fibers is to heat the moist nascent web 102. The papermaking machines
700, 702 of the fourth arrangement are similar to the papermaking
machines 600, 602 (see Figures 6A and 6B, respectively) of the third arrangement,
but includes features to heat the moist nascent web 102.
[0054] In this arrangement, the vacuum box 720 is a dual zone vacuum box, having a first
vacuum zone 722 and a second vacuum zone 724. The first vacuum zone 722 is positioned
opposite to the backing roll 312 or roll 532 and is used to transfer the moist nascent
web 102 from the backing roll 312 or transfer fabric 512 to the molding roll 610.
The first vacuum zone 722 is preferably shorter and uses a greater vacuum than the
second vacuum zone 724. The first vacuum zone 722 is preferably less than about two
inches and preferably draws a vacuum between about two inches of mercury and about
twenty-five inches of mercury.
[0055] In this arrangement, the nascent web 102 is heated on the molding roll 610 using
a steam shower 730. Any suitable steam shower 730 may be used with my invention including,
for example, a Lazy Steam injector manufactured by Wells Enterprises of Seattle Washington.
The steam shower 730 is positioned proximate to the molding nip 710 and opposite to
the second vacuum zone 724 of the vacuum box 720. The steam shower 730 generates steam
(for example saturated or superheated steam). The steam shower 730 directs the steam
toward the moist nascent web 102 on the patterned surface 612 of the molding roll
610 and the second vacuum zone 724 of the vacuum box 720 uses a vacuum to draw the
steam though the web 102, thus, heating the web 102 and the papermaking fibers therein.
The second vacuum zone 724 is preferably from about two inches to about twenty-eight
inches and preferably draws a vacuum between about five inches of mercury and about
twenty-five 5 inches of mercury. Although, the steam shower 730 may be suitably used
without a vacuum zone. The temperature of the steam is preferably from about two hundred
twelve degrees Fahrenheit to about two hundred twenty degrees Fahrenheit. Any suitable
heated fluid may be emitted by the steam shower, including, for example, heated air
or other gas. Heating the moist nascent web 102 in the molding nip 710 is not limited
to a heated fluid emitted from a steam shower 730. Instead, other techniques to heat
the moist nascent web 102 may be used including, for example, heated air, a heated
backing roll 312, or heating the molding roll 420, 520, 610 itself. The molding roll
420, 520, 610, and in particular the molding roll 420, 520 of the first and second
arrangements, may be heated like the backing roll 312 by using any suitable means
including, for example, steam or induction heating. By using air, for example, the
moist nascent web 102 may be heated and dried while being molded on the molding rolls
420, 520 of the first and second arrangements.
V. Fifth Arrangement of a Papermaking Machine
[0056] Figure 8 shows a fifth arrangement. The papermaking machine 800 of the fifth arrangement
is similar to the papermaking machine 600 (see Figure 6A) of the third arrangement,
but includes a doctor blade 810 at the molding zone 820. The doctor blade 810 is used
to peel the web from the backing roll 312 and to facilitate transfer of the web 102
to the molding roll 610. When the sheet is removed from the backing roll 312, by the
doctor blade 810, it introduces crepe to the web, which is known to increase sheet
caliper and bulk. Thus, implementation of this arrangement provides the ability to
add additional bulk to the overall process. Furthermore, sheet transfer by the doctor
blade 810 removes the need for contact between the backing roll 312 and the molding
roll 610 because the vacuum box 614 in the molding roll 610 will effect sheet transfer
to the patterned surface 612 without roll contact. By removing the need for roll to
roll contact to effect sheet transfer, roll wear is reduced, especially when there
are speed differences between the rolls. The doctor blade 810 may oscillate to further
crepe the web 102 at the molding zone 820. Any suitable doctor blade 810 may be used
with my invention, including, for example, the doctor blade disclosed in
U.S. Patent No. 6,113,470 (the disclosure of which is incorporated by reference in its entirety).
VI. Sixth Arrangement of a Papermaking Machine
[0057] Figures 9A and 9B show a sixth arrangement. The papermaking machines 900, 902 of
the sixth arrangement are similar to the papermaking machines 600, 602 of the third
arrangement (Figures 6A and 6B, respectively). Instead of the molding roll having
a patterned outer surface (e.g., permeable patterned surface 612 of the molding roll
610 in Figures 6A and 6B), a molding fabric 910 is used and the molding fabric 910
is patterned to impart structure to the moist nascent web 102 like the permeable patterned
surface 612
discussed in the third, fourth, and fifth arrangements. The molding fabric 910 is
supported on one end by a molding roll 920 and a support roll 930 on the other end.
The molding roll 920 has a permeable shell 922 (as will be discussed further below).
The permeable shell 922 allows a vacuum box 614 and a blow box 616 to be used, as
discussed above in the third arrangement.
[0058] As with the previous arrangements, this arrangement includes a cleaning section 940.
[0059] Because of the additional space afforded by the molding fabric 910, the cleaning
section 940 may be located on the fabric run between the molding roll 920 and the
support roll 930. Any suitable cleaning device may be used. Similar to the third arrangement,
a shower 942 enclosed in a receptacle 945 may be positioned on an interior of the
fabric run to direct water and/or a cleaning solution outward through the molding
fabric 910. A vacuum box 944 may be located opposite to the shower 942 to collect
the water and/or cleaning solution. Similar to the first and second arrangements,
a needle jet may also be used in an enclosure 948 to direct water and/or a cleaning
solution at an angle from a nozzle 946. Enclosure 948 maybe under vacuum to collect
the solution emitted by the spray nozzle 946.
VII. Seventh Arrangement of a Papermaking Machine
[0060] Figures 10A and 10B show a seventh arrangement. The papermaking machine 1000 shown
in Figure 10A is similar to the papermaking machine 400 of the first arrangement.
Likewise, the papermaking machine 1002 shown in Figure 10B is similar to the papermaking
machine 500 of the second arrangement. In these papermaking machines 1000, 1002, two
molding rolls 1010, 1020 are used instead of one. The first molding roll 1010 is used
to structure one side (a first side 104) of the paper web 102 using a patterned surface
1012, and the second molding roll 1020 is used to structure the other side (a second
side 106) using a patterned surface 1022. Molding both surfaces of the web 102 may
have several advantages; for example, it may be possible to achieve the benefits of
a two-ply paper 5 product with only a single ply, since each side of the sheet can
be independently controlled by the two molding rolls 1010, 1020. Also, individually
molding each side of the paper web 102 may also help to reduce sidedness. In the papermaking
machine 1002 shown in Figure 10B, having two molding rolls 1010, 1020 also enables
the wet web 102 to be directly transferred to the first molding roll 1010 from the
second forming fabric 206 and the transfer 10 fabric 512 of Figure 5 to be omitted.
[0061] As discussed above in the second arrangement, I have found that the molded structure
imparted to the paper web 102 by each molding roll 1010, 1020 may not continue through
the full thickness of the paper web 102. The sheet properties of each side of the
paper web 102 may thus be individually controlled by the corresponding molding roll
1010, 1020. For example, the patterned surfaces 1012, 1022 of each molding roll 1010,
1020 may have a different construction and/or pattern to impart a different structure
to each side of the paper web 102. Although there are advantages to constructing each
molding roll 1010, 1020 differently, the construction is not so limited, and the molding
rolls 1010, 1020, particularly, the patterned surfaces 1012, 1022, may be constructed
the same.
[0062] Sidedness can be counteracted by individually controlling the structure of each side
of the molded paper web 102 with the two different molding rolls 1010, 1020 of this
arrangement. For example, the patterned surface 1012 of the first molding roll 1010
may have deeper pockets and higher projections than the patterned surface 1022 of
the second molding roll 1020. In this way, the first side 104 of the paper web 102
will have recesses and protrusions that are deeper and higher than the second side
106 of the paper web 102 prior to the paper web 102 being applied to the Yankee drum
142. Then, when the first side 104 of the paper web 102 is applied to the Yankee drum
142, the Yankee drum 142 will smooth the first side 104 of the paper web 102 by reducing
the height of the protrusions such that, when the paper web 102 is peeled from the
Yankee drum 142 by the doctor blade 152, both the first and 30 second sides 104, 106
of the paper web 102 have substantially the same properties. For example, a user may
perceive that both sides have the same roughness and softness, or commonly measured
paper properties are within normal control tolerances for the paper product.
[0063] In this arrangement, the paper web 102 is transferred from the backing roll 312 or
second forming fabric 206 in a first molding zone, which is a first molding nip 1030
in this arrangement. The same considerations that apply to the features of the molding
nips 430, 530 (see Figures 4 and 5) in the first and second arrangements apply to
the first molding nip 1030 of this arrangement.
[0064] After the first side 104 of the paper web 102 is molded by the first molding roll
1010, the paper web 102 is then transferred from the first molding roll 1010 to the
second molding roll 1020 in a second molding zone, which is a second molding nip 1040
in this arrangement. The paper web 102 may be transferred in both molding nips 1030,
1040 by, for example, rush transfer. Similar to Equations (I) and (2), the creping
ratio in this arrangement for each nip 1030, 1040 may be calculated according to Equations
(4) and (5) as:

where Si is the speed of the backing roll 312 or second forming fabric 206, So is
the speed of the first molding roll 1010 and S7 is the speed of the second molding
roll 1020. Preferably, the web 102 is creped in each of the two molding nips 1030,
1040 at a ratio of about five percent to about sixty percent. But, high degrees of
crepe can be employed, approaching or even exceeding one hundred percent. A unique
opportunity exists with two molding nips that can be used to further modify sheet
properties. Since each crepe ratio primarily affects the side of the sheet being molded
the two crepe ratios can be varied relative to each other to control or vary sheet
sidedness. Control systems can be used to monitor sheet properties and use these property
measurements to control individual crepe ratios as well as differences between the
two crepe ratios.
[0065] The paper web 102 is transferred from the second molding roll 1020 to the drying
section 440, 540 in transfer nip 1050. As shown in Figure 10A, the drying section
440 includes a Yankee dryer section 140, and the same considerations that apply to
the transfer nip 450 of the first arrangement apply (see Figure 4) to the transfer
nip 1050 of this arrangement. As shown in Figure 1 OB, a TAD drying section 540 is
used, and the same considerations that apply to the transfer nip 550 (see Figure 5)
of the second arrangement apply to the transfer nip 1050 of this arrangement.
VIIL Eighth Arrangement of a Papermaking Machine
[0066] Figures 11A and 11B show an eighth arrangement. The papermaking machines 1100, 1102
of the eighth arrangement are similar to the papermaking machines 1000, 1002 of the
seventh arrangement, but the two molding rolls 1110, 1120 of the eighth arrangement
are constructed similarly to the molding roll 610 of the third arrangement (see Figures
6A and 6B) instead of the molding rolls 420, 520 of the first and second 10arrangements.
The first molding roll 1110 has a permeable patterned surface 1112 and a vacuum box
1114. The moist nascent web 102 is transferred from the backing roll 312 or second
forming fabric 206 in a first molding zone, which is a first molding nip 1130 in this
arrangement, using any combination of vacuum transfer using the vacuum box 1114 of
the first molding roll 1110, rush transfer (see Equation (4)) or a doctor blade 810
(see Figure 8). The first molding nip 1130 may be operated similarly to the molding
nip 620 of the third arrangement.
[0067] After the first side 104 of the paper web 102 is molded on the first molding roll
1110, the paper web is transferred from the first molding roll 1110 to the second
molding roll 1120 in a second molding zone, which is a second molding nip 1140 in
this arrangement, using any combination of a vacuum transfer using vacuum box 1124
of the second molding roll 1120, pressure differential using blow box 1116 of the
first molding roll 1110, rush transfer (see Equation (5)). The second side 106 of
the paper web 102 is then molded on the permeable patterned surface 1122 of the second
molding roll 1120. The types of transfers used individually or in combination can
be varied to control sheet properties and sheet sidedness. The considerations and
parameters that apply to the blow box 616 and vacuum box 614 in the third arrangement
also apply to the blow box 1116 of the first molding roll 1110 and the vacuum box
1124 of the second molding roll 1120.
[0068] The paper web 102 is transferred from the second molding roll 1120 to the drying
section 440, 540 in transfer nip 1150. As shown in Figure 11 A, the drying section
440 includes a 30 Yankee dryer section 140. As shown in Figure 11B, a TAD drying section
540 is used. Thesame considerations that apply to the features of the transfer nip
630 in the third arrangement apply to the transfer nip 1150 of this arrangement, including
the use of a blow box 1126 (similar to blow box 616) in the second molding roll 1120.
IX. Adjustment of Process Parameters to Control Fibrous Sheet Properties
[0069] Various properties of the resultant fibrous sheet (also referred to herein as paper
properties or web properties) can be measured by techniques known in the art. Some
properties may be measured in real time, while the paper web 102 is being processed.
For example, moisture content and basis weight of the paper web 102 may be measured
by a web property scanner positioned after the Yankee drum 142 and before the parent
roll 190. Any suitable web 10 property scanner known in the art may be used, such
as an MXProLine scanner manufactured by Honeywell of Morristown, NJ, that is used
to measure the moisture content with beta radiation and basis weight with gamma radiation.
Other properties, for example, tensile strength (both wet and dry), caliper, and roughness,
are more suitably measured offline. Such offline measurements can be conducted by
taking a sample of the paper web 102 as it is produced on the paper machine and measuring
the property in parallel with production or by taking a sample from the parent roll
190 and measuring the property after the parent roll 190 has been removed from the
paper machine.
[0070] As discussed above in the first through the eighth arrangements, various process
parameters can be adjusted to have an impact on the resulting fibrous sheet. These
process parameters 20include, for example: the consistency of the moist nascent web
102 at the molding nips 430, 530, 620, 710, 1030, 1040, 1130, 1140 or molding zone
820; creping ratios; the load at the molding nips 430, 530, 620, 710, 1030, 1040,
1130, 1140; the vacuum drawn by vacuum boxes 614, 720, 1114, 1124; and the air pressure
generated by blow boxes 616, 1116, 1126. Typically, a measured value for each paper
property of the resultant fibrous sheet lies within a desired range for that paper
property. The desired range will vary depending upon the end product of the paper
web 102. If a measured value for a paper property falls outside the desired range,
an operator can adjust the various process parameters of this invention so that, in
a subsequent measurement of the paper property, the measured value is within the desired
range.The vacuum drawn by vacuum boxes 614, 720, 1114, 1124 and the air pressure generated
by blow boxes 616, 1116, 1126 are process parameters that can be readily and easily
adjusted while the paper machine is in operation. As a result, the papermaking processes
of my invention, in particular those described in arrangements three through six and
eight, may be advantageously used to make consistent fibrous sheet products by real
time or near real time adjustment to the papermaking process.
X. Construction of the Permeable Molding Roll
[0071] I will now describe the construction of the permeable molding roll 610, 920, 1110,
1120 used with the papermaking machines of the third through sixth and eighth arrangements.
For 10 simplicity, the reference numerals used to describe the molding roll 610 (Figures
6A and 6B) of the third arrangement above will be used to describe corresponding features
below. Figure 12 is a perspective view of the molding roll 610, and Figure 13 is a
cross-sectional view of the molding roll 610 shown in Figure 12 taken along the plane
13-13. The molding roll 610 has a radial direction and a cylindrical shape with a
circumferential direction C (see Figure 14) that corresponds to the MD direction of
the papermaking machine 600. The molding roll 610 also has a length direction L (see
Figure 13) that corresponds to the CD direction of the papermaking machine 600. The
molding roll 610 may be driven on one end, the driven end 1210. Any suitable method
known in the art may be used to drive the driven end 1210 of the molding roll 610.
The other end of the molding roll 610, the rotary end 1220, is supported by 20 and
rotates about a shaft 1230. The driven end 1210 includes a driven endplate 1212 and
a shaft 1214, which may be driven. The rotary end 1220 includes a rotary endplate
1222. In this arrangement, the driven endplate 1212 and the rotary endplate 1222 are
constructed from steel, which is a relatively inexpensive structural material. Although,
those skilled in the art will recognize that the endplates 1212, 1222 may be constructed
from any suitable structural material. The rotary plate 1222 is attached to the shaft
1230 by a bearing 1224. A permeable shell 1310 is attached to the circumference of
each of the driven endplate 1212 and the rotary endplate 1222 forming a void 1320
there between. The permeable patterned surface 612 is formed on the exterior of the
permeable shell 1310. The details of the permeable shell 1310 will be discussed further
below. The vacuum box 614 and the blow box 616 are located in the void 1320 and are
supported by shaft 1230 and a rotary connection 1352 to driven endplate 1212 through
support structure 1354. Support structure 1354 allows both vacuum and pressurized
air to be conveyed to vacuum box 614 and blow box 616, respectively, through the shaft
1230. Both the vacuum box 614 and the blow box 616 are stationary, and the permeable
shell 1310 rotates around the stationary boxes 614, 616. Although Figure 13 shows
these boxes to be opposite to each other on the roll, it is recognized that they can
be disposed at any angle around the roll circumference as needed to carry out their
functions. Vacuum is drawn in vacuum box 614 through the use of a vacuum line 1332
that is part of the box support structure 1354. A vacuum pump 1334 thus is able to
apply a vacuum to the vacuum box 614 via vacuum line 1332. Similarly, a pump or blower
1344 is used to force air through pressure line 1342 to 10 create a positive pressure
in blow box 616.
[0072] Figure 14 shows cross section of the permeable shell 1310 and vacuum box 614, taken
along line 14-14 in Figure 13. The blow box 616 is constructed in substantially the
same way as is the vacuum box 614. As shown in Figure 14, the vacuum box 614 is substantially
u-shaped having a first top ends 1420 and a second top end 1430. An open portion extends
between the two top ends 1420, 1430 having a distance D in the circumferential (MD)
direction C of the molding roll 610. The distance D of the open portion forms the
vacuum zones discussed above. In this arrangement, the vacuum box 614 is constructed
from stainless steel with walls that are thick enough to accommodate the vacuum generated
in the cavity 1410 and to withstand the rigors of roll operation. Those skilled in
the art will recognize that any suitable 20 structural material can be used for the
vacuum box but, preferably, is one that is resistant to corrosion from moisture that
may be drawn from the web by the vacuum. In this arrangement, the vacuum box 614 is
depicted with one single cavity 1410 extending in the length (CD) direction L of the
molding roll 610. To draw a uniform vacuum across in the length (CD) direction L,
it may be desirable to subdivide the vacuum box 614 into multiple cavities 1410. Those
skilled in the art will recognize that any number of cavities may be used. Likewise,
it may be desirable to subdivide the vacuum box 614 into multiple cavities in the
circumferential (MD) direction C to form, for example, the two stage vacuum box discussed
above.
[0073] A seal is formed between each end 1420, 1430 of the vacuum box 614 and an inside
surface 30 of the permeable shell 1310. In this arrangement, a tube 1422 is positioned
in a cavity formed in the first top end 1420 of the vacuum box 614. Pressure is applied
to inflate the tube 1422 and to press a sealing block 1424 against the inside surface
of the permeable shell 1310. Likewise, two tubes 1432 are positioned inside cavities
formed in the second top end 1430 and used to press a sealing block 1434 against the
inside surface of the permeable shell 1310. In addition, an internal roll shower 1440
may be positioned upstream of the vacuum box to apply a lubricating material, such
as water, to the bottom surface of the permeable shell 1310, thereby reducing frictional
forces and wear between the sealing blocks 1424, 1434 and the permeable shell 1310.
Similarly, each end in the CD direction of the vacuum box 614 and blow box 616 are
sealed. As may be seen in Figure 13, a tube 1362 is positioned in a cavity formed
in the ends of the vacuum box 614 and blow box 616 and inflated to press 10 a sealing
block 1364 against the inside surface of the permeable shell 1310. Any suitable wear
material, such as polypropylene or a polytetrafluoroethylene impregnated polymer,
may be used as the sealing blocks 1364, 1424, and 1434. Any suitable inflatable material,
such a rubber, may be used for the tubes 1362, 1422, 1432.
[0074] Figures 15A through 15E are arrangements of the permeable shell 1310 showing detail
15 in Figure 14. Figures 15 A, 15B, and 15C show a two layer construction of the permeable
shell 1310. The inner most layer is structural layer 1510, and the outer layer is
a molding layer 1520.
[0075] The structural layer 1510 provides the permeable shell 1310 support. In this arrangement,
the structural layer 1510 is made from stainless steel, but any suitable structural
material may be 20 used. The thickness of the shell is designed to withstand the forces
exerted during paper production, including, for example, the forces exerted when the
molding nip 620 in the third arrangement is a pressure nip. The thickness of the structural
layer 1510 is designed to withstand the loads on the roll to avoid fatigue and other
failure. For example, the thickness will depend on the length of the roll, the diameter
of the roll, the materials used, the density of channels 1512, and the loads applied.
Finite element analysis can be used to determine practical roll design parameters
and roll crown, if needed. The structural layer 1510 has a plurality of channels 1512.
The plurality of channels 1512 connects the outer layer of the permeable shell 1310
with the inside of the molding roll 610. When a vacuum is drawn or a pressure is exerted
from either of the vacuum box 614 or blow box 616, respectively, the air 30 is pulled
or pushed through the plurality of channels 1512.
[0076] The molding layer 1520 is patterned to redistribute and to orient the fibers of the
web 102 as discussed above. In the third arrangement, for example, the molding layer
1520 is the permeable patterned surface 612 of the molding roll 610. As discussed
above, my invention is particularly suited for producing absorbent paper products,
such as tissue and towel products. Thus, to enhance the benefits in bulk and absorbency,
the molding layer 1520 is preferably patterned on a fine scale suitable to orient
fibers of the web 102. The density of each of the pockets and projections of the molding
layer 1520 is preferably greater than about fifty per 0.00064516 square meter (about
fifty per square inch) and more preferably greater than about two hundred per 0.00064516
square meter (about two hundred per square inch).
[0077] Figure 16 is an example of a preferred plastic, woven fabric that may be used as
the molding 10 layer 1520. In this arrangement, the woven fabric is shrunk around
the structural layer 1510. The fabric is mounted in the apparatus as the molding layer
1520 such that its MD knuckles 1600, 1602, 1604, 1606, 1608, 1610 and so forth extend
along the machine direction of the papermaking machine (e.g., 600 in Figure 6A). The
fabric may be a multi-layer fabric having creping pockets 1620, 1622, 1624, and so
forth, between the MD knuckles of the fabric. A plurality of CD knuckles 1630, 1632,
1634, and so forth, is also provided, which may be preferably recessed slightly with
respect to the MD knuckles 1600, 1602, 1604, 1606, 1608, 1610 of the creping fabric.
The CD knuckles 1630, 1632, 1634 may be recessed with respect to the MD knuckles 1600,
1602, 1604, 1606, 1608, 1610 a distance of from about 0.1 mm to about 0.3 mm. This
geometry creates a unique distribution of fiber when the web 102 is wet 20 molded
from the backing roll 312 or transfer fabric 512, as discussed above. Without intending
to be bound by theory, it is believed that the structure illustrated, with relatively
large recessed "pockets" and limited knuckle length and height in the CD, redistributes
the fiber upon high impact creping to produce a sheet, which is especially suitable
for recycle furnish and provides surprising caliper. In the sixth arrangement, the
molding layer 1520 is not attached to the structural layer 1510 and is the molding
fabric 910 shown in Figures 9A and 9B.
[0078] The molding layer 1520 is not limited, however, to woven structures. For example,
the molding layer 1520 may be a layer of plastic or metal that has been patterned
by knurling, laser drilling, etching, machining, embossing, and the like. The layer
of plastic or metal may 30 be suitably patterned either before or after it is applied
to the structural layer 1510 of molding roll 610.
[0079] Referring back to Figure 15 A, the spacing and diameter of the plurality of channels
1512 are preferably designed to provide a relatively uniform vacuum or air pressure
at the roll surface of the molding layer 1520. To aid in applying uniform pressure,
grooves 1514 that extend or radiate from the plurality of channels 1512 may be cut
in the outer surface of the structural layer 1510. Although, other suitable channel
designs may be used to assist in spreading the suction or air pressure under the molding
layer 1520. For example, the top edge of the each channel 1512 may have a chamfer
1516, as shown in Figure 15B. In addition, the channel 1512 geometry is not limited
to right, circular cylinders. Instead, other suitable geometries may be used including,
for example, a right, trapezoidal cylinder, as shown in Figure 15C, which may be formed
when the plurality of channels 1512 is created by laser drilling.
[0080] The plurality of channels 1512 preferably have a construction consistent with the
structural needs of the permeable shell 1310 and the ability to uniformly apply vacuum
or pressure to the molding surface to effect sheet transfer and molding. In the arrangements
shown in Figure 15 A, 15B, and 15C, the plurality of channels 1512 preferably has
a mean diameter from about two hundredths of an inch to about a half of an inch, more
preferably from about sixty-two thousandths of an inch to about a quarter of an inch.
In calculating the mean diameter, the diameter of the grooves 1514 and chamfer 1516
may be excluded. Each channel 1512 is preferably spaced from about sixty-four thousandths
of an inch to about three hundred seventy-five thousandths of an inch from the next
closest channel 1512, more 20 preferably from about one hundred twenty-five thousandths
of an inch to about a quarter of an inch. Additionally, the structural layer 1510
preferably has a density of between about fifty channels per fifty per 0.00064516
square meter (about fifty per square inch) to about five hundred channels per 0.00064516
square meter (five hundred per square inch). The closer spaced channels and higher
channel densities may achieve a better, more uniform distribution of air. It may be
difficult, however, to achieve a sufficient density of the plurality of channels 1512
to apply uniform air pressure to the molding layer 1520 and still have the structural
layer provide sufficient structural support with the arrangement shown in Figure 15
A. To alleviate this concern, an air distribution layer 1530 may be used as a middle
layer, as shown in Figure 15D. The air distribution layer 1530 is preferably formed
by a permeable material that allows the air pushed or drawn through the plurality
of channels 1512 to spread under the molding layer 1520, thus creating a generally
uniform draw or pressure. Any suitable material may beused including, for example,
porous sintered metals, sintered polymers, and polymer foams. Preferably, the thickness
of the air distribution layer 1530 is from about one tenth of an inch to about one
inch, more preferably about an eighth of an inch to about a half of an inch.
[0081] When the air distribution layer 1530 is used, the density of the plurality of channels
1512 may be spread out and the diameters increased. In the arrangement shown in Figure
15D, the plurality of channels 1512 preferably has a diameter from about two hundredths
of an inch to about five tenths of an inch, more preferably from about five hundredths
of an inch to about a quarter of an inch. Each channel 1512 is preferably spaced from
about five hundredths of an inch to about one inch from the next closet channel 1512,
more preferably from about on 10 tenth of an inch to about five tenths of an inch.
Additionally, the structural layer 1510 preferably has a density of between about
fifty channels 1512 per 0.00064516 square meter (about fifty channels 1512 per square
inch) to about three hundred channels 1512 per 0.00064516 square meter (three hundred
channels per square inch).
[0082] As shown in Figure 15E, a separate molding layer 1520 may not be necessary. Instead,
the outer surface 1518 of the structural layer 1510 may be textured or patterned to
form the 15 permeable patterned surface 612. In the arrangement shown in Figure 15E,
the outer surface 1518 is patterned by knurling, but any suitable method known in
the art, including, for example, laser drilling, etching, embossing, or machining,
may be used to texture or to pattern the outer surface 1518. Although 15E shows patterning
on top of a drilled shell it is also possible to apply patterning by knurling, laser
drilling, etching, embossing, or machining 20 the outer surface of the air distribution
layer 1530 or molding layer 1520, as discussed above.
[0083] Figure 17 shows a top view of a knurled outer surface 1518, and the section shown
in Figure 15E is taken along line 15E-15E shown in Figure 17. While any suitable pattern
may be used, the knurled surface has a plurality projections 1710, which in this arrangement,
are pyramid shaped. The pyramid-shaped projections 1710 of this arrangement have a
major axis extending in the MD direction of the molding roll 610 and a minor axis
extending in the CD direction of the molding roll 610. The major axis is longer than
the minor axis, giving the base 1712 of the pyramid-shaped projections 1710 a diamond
shape. The pyramid-shaped projections 1710 have four lateral sides 1714 that angle
and extend downward from the pinnacle 1716 to the base 1712. Thus, the area where
four vertices of four different pyramid- 30 shaped projections 1710 come together
forms a recess or pocket 1720. The pyramid-shaped projections 1710 and pockets 1720
of the knurled outer surface 1518 redistribute thepapermaking fibers to mold and to
form inverse recesses and protrusions on the paper web 102.
[0084] The pyramid-shaped projections 1710 are separated by grooves 1730. The grooves 1730
of the knurled outer surface 1518 are similar to the grooves 1514 described above
with reference to Figure 15A. The grooves 1730 radiate outward from a channel 1512
to distribute the air being pushed or pulled through the channels 1512 across the
knurled outer surface 1518 and help to evenly distribute the air across the knurled
outer surface 1518.
XI. Construction of the Non-Permeable Molding Roll
[0085] I will now describe the construction of the non-permeable molding roll 420, 520,
1010, 1020 10 used with the papermaking machines of the first, second, and seventh
arrangements. For simplicity, the reference numerals used to describe the molding
roll 420 of the first arrangement above will be used to describe corresponding features
below. Figure 18 is a perspective view of the non-permeable molding roll 420. As with
the permeable molding roll 610, described above, the non-permeable molding roll 420
has a radial direction and a cylindrical shape with a circumferential direction that
corresponds to the MD direction of the papermaking machine 400. The molding roll 420
also has a length direction that corresponds to the CD direction of the papermaking
machine 400.
[0086] The non-permeable molding roll 420 has a first end 1810 and a second end 1820. Either
one or both of the first or second ends 1810, 1820 may be driven by any suitable means
known in the art. In this arrangement, both ends have shafts 1814, 1824 that are,
respectively, connected to endplates 1812, 1822. The end plates 1812, 1822 support
each end of a shell (not shown) on which the patterned surface 422 is formed. The
roll may be made from any suitable structural material known in the art including,
for example, steel. The shell forms the structural support for the patterned surface
422 and may be constructed as a stainless steel cylinder, similar to the permeable
shell 1310 discussed above but without the channels 1512.
[0087] The molding roll 420, however, is not limited to this construction. Any suitable
roll construction known in the art may be used to construct the non-permeable molding
roll 420. The patterned surface 422 may be formed similarly to the molding layer 1520
discussed above. For example, the patterned surface 422 may be formed by a woven fabric
(such as the fabric discussed above with reference to Figure 14) that is shrunk around
the shell of the non-permeable molding roll. In another example, the outer surface
of the shell may be textured or patterned. Any suitable method known in the art, including,
for example, knurling (such as the knurling discussed above with reference to Figure
17), etching, embossing, or machining, may be used to texture or pattern the outer
surface. The patterned surface 422 may also be formed by laser drilling or etching
and, in such a case, is preferably formed from an elastomeric plastic, but any suitable
material may be used.
[0088] Although this invention has been described in certain specific exemplary arrangements,
many additional modifications and variations would be apparent to those skilled in
the art in light of this disclosure. It is, therefore, to be understood that this
invention may be practiced 10 otherwise than as specifically described. Thus, the
exemplary arrangements of the invention should be considered in all respects to be
illustrative and not restrictive and the scope of the invention to be determined by
any claims supportable by this application and the equivalents thereof, rather than
by the foregoing description.
INDUSTRIAL APPLICABILITY
[0089] The invention can be used to produce desirable paper products, such as paper towels
and bath tissue. Thus, the invention is applicable to the paper products industry.
[0090] FURTHER EMBODIMENTS OF THE PRESENT INVENTION MAY BE AS FOLLOWS:
- 1. A roll for molding a fibrous sheet, the roll comprising:
a cylindrical shell configured to be rotatably driven in a circumferential direction,
the cylindrical shell including an interior surface, an exterior surface, and a permeable
patterned surface on the exterior surface of the cylindrical shell, the cylindrical
shell being permeable to allow air to be moved through the cylindrical shell, the
permeable patterned surface has at least one of a plurality of recesses and a plurality
of projections, the density of the at least one of the plurality of recesses and the
plurality of projections being greater than about fifty per square inch; and
a vacuum box positioned on the inside of the cylindrical shell and being configured
to draw air from the exterior surface of the cylindrical shell to the interior surface
of the cylindrical shell, the vacuum box being stationary with respect to the rotation
of the cylindrical shell.
- 2. The roll of embodiment 1, further comprising a vacuum pump being connected to the
vacuum box, wherein the vacuum pump is used to draw air from the exterior surface
of the cylindrical shell to the interior surface of the cylindrical shell.
- 3. The roll of embodiment 1, further comprising a blow box positioned on the inside
of the cylindrical shell and being configured to push air from the interior surface
of the cylindrical shell to the exterior surface of the cylindrical shell, the blow
box being stationary with respect to the rotation of the cylindrical shell.
- 4. The roll of embodiment 3, further comprising a pump being connected to the blow
box, wherein the pump is used to push air from the interior surface of the cylindrical
shell to the exterior surface of the cylindrical shell.
- 5. The roll of embodiment 1, wherein the density of the at least one of the plurality
of recesses and the plurality of projections is greater than about two hundred per
square inch.
- 6. The roll of embodiment 1, wherein the permeable patterned surface is formed by
at least one of knurling, laser drilling, etching, embossing, and machining the exterior
surface of the cylindrical shell.
- 7. The roll of embodiment 1, wherein the cylindrical shell further includes a structural
layer, the structural layer having a plurality of channels through the thickness of
the structural layer, the plurality of channels being configured to allow air to be
moved through the structural layer.
- 8. The roll of embodiment 7, wherein the permeable patterned surface is a molding
layer formed on an exterior surface of the structural layer,
- 9. The roll of embodiment 8, wherein the molding layer comprises a woven structure
adapted for enhancing sheet properties.
- 10. The roll of embodiment 7, further comprising an air distribution layer located
between the structural layer and the molding layer, the air distribution layer being
permeable to distribute under the molding layer air moved through the structural layer.
- 11. The roll of embodiment 10, wherein the air distribution layer comprises at least
one of sintered metals, sintered polymers, and polymer foams.
- 12. The roll of embodiment 1, wherein the permeable patterned surface is a fabric
supported by the structural layer.
- 13. The roll of embodiment 7, further comprising a plurality of grooves extending
from each of the plurality of channels, the plurality of grooves being configured
to distribute under the molding layer air moved through the structural layer.
- 14. The roll of embodiment 7, wherein each of the plurality of channels has an interior
end, an exterior end, and a chamfer on the exterior end.
- 15. The roll of embodiment 7, wherein each of the plurality of channels is at least
one of a right, circular cylinder and a right, trapezoidal cylinder.
- 16. The roll of embodiment 1, further comprising a cleaning section positioned on
the inside of the cylindrical shell and being configured to direct a cleaning medium
from the interior surface of the cylindrical shell to the exterior surface of the
cylindrical shell.
- 17. The roll of embodiment 16, wherein the cleaning section includes a shower and
the cleaning medium includes at least one of water and a cleaning solution.